Drive assembly with compensation for misalignment

ABSTRACT

A drive shaft has a bore formed at its outer facing end. An annular adapter element has a series of external splines which interfit with internal splines in the bore of the drive shaft. The adapter element has a bore with internal splines that interfit with external splines on a driven shaft received in the adapter bore. The internal splines between the drive shaft and the external splines on the adapter element are lubricated so that the adapter element rocks preferentially relative to the drive shaft to compensate for angular misalignment. The adapter element is retained relative to the drive shaft and a seal is provided between them so that the driven shaft may be removed without exposing the lubrication system for the spline. In another form an elongated tubular element is placed between the adapter and the drive shaft to compensate for both parallel and angular misalignment.

United tates Stein atent [191 DRIVE ASSEMBLY WITH COMPENSATION FORMISALIGNMENT [52] U.S. Cl. 64/9 R, 184/611 [51] Int. Cl. F1611 3/46 [581Field of Search 64/6, 9 R, 16;

184/1 R, 6.11; 287/53 SS [56] References Cited UNITED STATES PATENTS3,132,494 5/1964 Hoffer 64/9 R 2,982,117 5/1961 Erpenstein 64/9 R2,885,232 5/1959 Eberly 64/9 R X 3,375,901 4/1968 Farrell 184/1 R 1Sept. 11, 1973 Primary ExaminerManuel A. Antonakas Attorney-Charles M.Hogan et al.

[57] ABSTRACT A drive shaft has a bore formed at its outer facing end.An annular adapter element has a series of external splines whichinterfit with internal splines in the bore of the drive shaft. Theadapter element has a bore with internal splines that interfit withexternal splines on a driven shaft received in the adapter bore. Theinternal splines between the drive shaft and the external splines on theadapter element are lubricated so that the adapter element rockspreferentially relative to the drive shaft to compensate for angularmisalignment. The adapter element is retained relative to the driveshaft and a seal is provided between them so that the driven shaft maybe removed without exposing the lubrication system for the spline. Inanother form an elongated tubular element is placed between the adapterand the drive shaft to compensate for both parallel and angularmisalignment.

13 Claims, 2 Drawing Figures Patented Sept. 11, 1973 3,757,535

INVENTOR.

WOLFGANG J. STEIN ATTORNEYS.

DRIVE ASSEMBLY WITH COMPENSATION FOR MISALIGNMENT The present inventionrelates to drive assemblies and more specifically to drive assembliesthat compensate for misalignment.

There have been many drive assemblies proposed in the past thatcompensate for misalignment between drive and driven shafts. For themost part they are bulky and complicated devices that greatly add to thecomplexity, cost and weight of the drive assembly. This is a greatdisadvantage when the drive assembly is incorporated in a gas turbineaircraft-type engine. An additional disadvantage of the prior art drivearrangements is that in some cases the interior of a gear box with whichthe drive is used is exposed when the driven shaft is removed. Theexposure of the interior of the gear box greatly increases thepossibility of contaminants.

Therefore it is an object of the present invention to provide a highlysimplified, effective and economical drive assembly that compensates formisalignment.

This end is achieved by an annular adapter element having externalsplines which interfit with internal splines in a bore of a drive shaftmeans. The adapter element has internal directed splines on its own borewhich interfit with external splines on a driven shaft received in theadapter bore. The coefficient of friction between the internal splineson the drive shaft means and the external splines on the adapter ismaintained at a level lower than the coefficient of friction between theadapter element and the driven shaft so that the adapter rockspreferentially relative to the drive shaft to compensate formisalignment.

The above and other related objects and features of the presentinvention will be apparent from a reading of the description of thedisclosure shown'in the accompanying drawing and the novelty thereofpointed out in the appended claims.

In the drawing:

FIG. 1 is a drive assembly embodying the present invention and adaptedto compensate for angular misalignment;

FIG. 2 is another drive assembly embodying the present invention andadapted to compensate for both angular and parallel misalignment.

Referring to FIG. 1 there is shown a drive assembly incorporated in anouter housing 10. A bearing assembly 12 secured in housing journals adrive shaft 14. A shoulder on shaft 14 abuts one side of the inner raceof bearing assembly 12. A combination seal and spacer assembly 22 abutsthe opposite side of the inner race. An annular retaining ring 24 abutsseal element 22 and nut 26 sandwiches these elements together andretains them on shaft 14.

To simplify the discussion of the present invention the means fordriving the shaft, in addition to the means for journaling the shaft 14in addition to the bearing assembly, will not be shown. It should beapparent to those skilled in the art that many different arrangementscan be utilized for this purpose.

An outer facing end 16 of shaft 14 faces the exterior of the housing 10through a generally annular opening 18 formed generally in line with theouter facing end of shaft 14. Shaft 14 has a bore 28 formed in its outerfacing end and a series of internal splines 30 are formed in this bore.An annular adapter element 32 is received in bore 28. Adapter element 32has external splines 34 formed around its periphery and these splinesinterfit with the splines 30 on the interior wall of bore 28. Adapterelement 32 has an internal bore 36 opened to the exterior of housing 10.

As herein shown, adapter element 32 is in a tubular form and has a disk38 on the interior end of the tubular element to seal off the interiorof the gear box from the exterior. However, it should be apparent thatthe adapter element may be formed by a casting or other suitablearrangement. A series of inwardly directed splines 40 are formed on theinterior of bore 36. These splines receive interfitting splines 42 of adriven shaft 44.

For this particular arrangement driven shaft 44 extends to an accessory,positioned in housing 46. Driven shaft 44 is a generally long shaftsplined at both ends so that the only misalignment presented by drivenshaft 44 relative to drive shaft 14 is an angular misalignment.

The splines 30 and 34 are lubricated by means of lubricating fluid whichis discharged from nozzle 48 by means of a suitable pressurizing systemagainst the exterior of drive shaft 14. Suitable radial ports 50 (onlyone of which is shown) permit lubricating fluid to pass from the nozzle48 to an interior passage 52 extending to bore 28. Lubricating fluidthus passes into the splines 30, 34 between the adapter element 32 andthe bore 28 of thedrive shaft 14. This fluid is prevented from passingoutward between the adapter and the bore 28 by an O-ring 54 received inan annular groove 56. A scavenge flow of fluid through the splines ispromoted by means of a series of radially extending ports 58 whichextend from the innermost portion of the splines 30 or, in other words,the minor diameter of the internal spline in the interior of the shaft14 to the exterior thereof. An annular recess 60 and additional radialports 62 in the seal element 22 provide a passageway to the annularspace outside of the shaft 14. From there the lubricating fluid can bereturned to the pressurizing means by a suitable arrangement. A-stationary seal element, generally indicated by reference character 64,retained in opening 18 by retaining ring 66 cooperates with seal element22 to prevent leakage of lubricating fluid from the opening 18 by way ofthe exterior of shaft 14.

Element 32 is retained in place by an integral flange 23 which isreceived between the outer facing end 16 of shaft 14 and a flange 35integral with nut 26.

As the drive and driven shafts rotate, lubricating fluid enters theinterior of shaft 14 and passes to the splines 30 and 34 where it isscavenged through ports 58. Since ports 58 extend to the inner side ofsplines 30, substantially all of the annulus between the inner wall ofbore 28 and the base of the splines 34 is immersed in lubricating fluid.

During rotation the tangential forces at the spline surfaces create afriction force. The tangential force at the inner pair of splines 40 and42 is greater than the tangential force of splines 30 and 34 for a giventransmitted torque. This causes a reduced friction force at the exteriorsplines 30 and 34. However, the coefficient of friction in between thesplines 30 and 34 is maintained at a much lower level than that for theinner splines because of the lubricating fluid.

The substantial reduction in the coefficient of friction between thesplines 30 and 34 provided by the lubricating fluid causes the adapterelement 32 to rock preferentially relative to drive shaft 14 wheneverthere is an angular misalignment of driven shaft 44. Since the splines40 and 42 have a much greater coefficient of friction they resist anymovement of the adapter element 34 and therefore the adapter rocksrelative to the drive shaft rather than the driven shaft 44.

The only splines that are subjected to wear in this arrangement are thesplines 30 and 34. However, this wear is minimized due to thelubricating fluid. Furthermore, the reduced tangential force on thesplines 30 and 34 enables their length to be shorter than the length ofsplines 40 and 42 for a given torque capacity. The shorter splines 30and 34 can accommodate a greater angle of misalignment for a given driveassembly size.

The above arrangement is used in the case where angular misalignmentonly is compensated for. However, the arrangement shown in FIG. 2compensates not only angular but parallel misalignment of shafts. Thisgear arrangement comprises a housing 70 on which an outer drive shaft 72is journaled by space bearing assemblies 74 and 76. Outer drive shaft 72has an integral gear assembly (not shown) which receives a drive inputfrom a suitable gear, as will be apparent to those skilled in the art.An opening 78 is formed in housing 70 in line with the outer facing endof outer shaft 72. A suitable seal arrangement, generally indicated byreference character 80, seals the outer periphery of shaft 72 at opening78 to prevent leakage of lubricating fluid.

Outer drive shaft 72 has a through bore 82 having inwardly directedsplines 84 at the end of the shaft 72 away from opening 78. A generallytubular connecting element 86 is received within through bore 82 and hasexternal splines 87 which interfit with splines 84 on drive shaft 72. Aseries of inner splines 88 adjacent opening 78 receive outer splines 90on the periphery of an annular adapter element 92. Adapter element 92has a bore 94 with internal splines 96. Internal splines 96 interfitwith external splines 98 on a driven shaft 100 that is received withinbore 94.

An O-ring 102 received in groove 104 seals the space between adapterelement 92 and the tubular element 86. A second O-ring 106 received ingroove 108 seals the space between tubular element 86 and the throughbore 82 of outer shaft 72.

The axial movement of tubular shaft 86 is restrained by flanges 110 and112 thread onto opposite ends of outer drive shaft 72. The flangedelement 112 also restrains the movement of annular adapter element 92out of the opening 78.

Lubricating fluid is supplied to the interior of tubular element 86 viaa nozzle 114 by a suitable pressurizing device. A scavenge path for oilis provided from splines 84 and 87 by a series of radial ports 116extending from the minor diameter of internal splines 84 to a recess I18 formed in the exterior of shaft 72. Recess 1 18 connects with radialports I formed in a spacer sleeve I22 for discharge back to a suitablesump in the gear box.

In operation of this drive assembly lubricating fluid is directed intothe interior of tubular element 86. it forms an annular layer betweensplines 88 and 90 and also between splines 84 and 87. The flow throughsplines 84 and 87 is promoted by radial scavenging ports throughcentrifugal action. In a fashion similar to that for the coupling inFIG. 1 the spline pairs 84, 87 and 88, 90 rock rather than spline pairs96 and 98. This is due to the greatly reduced coefficient of frictionmaintained by the presence of the lubricating fluid. It

should be noted that this arrangement is particularly advantageous whenthe shaft 100 is a rigid shaft and not capable of angular movement. Ifshaft 100 is displaced laterally to the axis denoted by M, the tubularelement 86 rocks at the spline pairs 84, 87 and 88, for each revolutionof the assembly. This compensates for both angular and parallelmisalignment of the drive shaft 72 and the driven shaft 100.

in both of the arrangements described above the misalignment normallyfound between a driven and a drive shaft are compensated for by anextremely compact and simplified arrangement. It should be noted thatthe driven shafts in both assemblies can be withdrawn from the adapterelement without exposing the lubricating system for the coupling and forthe interior of the gear box. This greatly minimizes the possibilitiesof contaminating the gear box during removal of a driven item, such asan accessory.

While the preferred embodiment of the present invention has beendescribed, it should be apparent to those skilled in the art that othermodifications may be preformed without departing from its spirit andscope. Having thus described the invention what is claimed as novel anddesired to be secured by Letters Patent of the United States is:

l. A drive assembly comprising: a drive shaft having a bore at an outerfacing end thereof and internal splines formed in said bore;

an annular adapter element received in said drive shaft bore and havingexternal splines interfitting with the internal splines formed in saiddrive shaft bore;

said adapter element also having a bore with internal splines formedtherein to interfit with external splines of a driven shaft receivablein said adapter bore;

means for maintaining the coefficient of friction between the driveshaft splines and the adapter element external splines substantiallylower than the coefficient of friction between the adapter elementinternal splines and the splines of said driven shaft, said meanscomprising means for supplying lubricant to the interfitting internalsplines of said drive shaft and the external splines of said adapterelement whereby the adapter element rocks preferentially relative to thedrive shaft to compensate for misalignment between the drive shaft meansand said driven shaft.

2. A drive assembly as in claim 1 further comprising means forscavenging oil from said internal splines of said drive shaft whereby aflow of lubricating fluid passes through the splines of said driveshaft.

3. A drive assembly as in claim 2 wherein said scavenging meanscomprises a series of passageways extending generally radially outwardfrom the minor diameter of the internal splines to the exteriorperiphery of said drive shaft whereby the splines of said drive shaftand the outer splines of said adapter element are substantially immersedin lubricating fluid.

4. A drive assembly as in claim 1 further comprising:

a housing surrounding said drive shaft means and having an annularopening substantially in line with the outer facing end of said driveshaft;

means for sealing the outer periphery of said drive shaft relative tothe opening in said housing thereby preventing leakage of lubricatingfluid past the outer periphery of said drive shaft; and

means for sealing the outer periphery of said adapter element relativeto the bore of said drive shaft whereby the external splines on saidadapter element and the internal splines on said drive shaft areimmersed in lubricating fluid.

S. A drive assembly as in claim 4 further comprising:

a flange formed at the outer end of said adapter element for abuttingthe outer facing end of the said drive shaft; and

a retaining flange releasably secured over the outer facing end of saiddrive shaft for restraining movement of said adapter away from the outerfacing end of said drive shaft. 6. A drive assembly as in claim 5wherein said adapter element is formed from a sleevelike element havinga circular disk secured to the inner end of said element for preventingflow of oil to the internal splines of said adapter.

7. A drive assembly as in claim 6 wherein: said drive shaft has a seriesof radially directed holes extending from the minor diameter of theinternal splines of said drive shaft to the exterior periphery thereof;a

said lubricating means comprises ajet adapted to discharge a supply oflubricating fluid against the exterior of said drive shaft at a positionspaced from said splines, said drive shaft having a generally radialopening in line with said jet thereby permitting flow of lubricatingfluid to the interior bore of said drive shaft 8. A drive assemblycomprising:

an outer elongated annular drive shaft having a first end adjacent saidadapter element and having a plurality of internal splines formed at asecond end axially spaced from said first end;

an elongated tubular element received in the interior of said outerdrive shaft and having exterior splines at one end interfitting with theinterior splines on said outer shaft and inwardly directed splines atthe opposite end thereof;

an annular adapter element received insaid tubular element at theopposite end thereof and having external splines interfltting with theinternal splines formed in said drive shaft bore;

said adapter element also having a bore with internal splines formedtherein to interfit with external splines of a driven shaft receivablein said adapter bore; and means for maintaining the coefficient offriction between the drive shaft splines and the adapter elementexternal splines substantially lower than the 5 coefficient of frictionbetween the adapter element internal splines and the splines of saiddriven shaft whereby the adapter element rocks preferentially relativeto the drive shaft to compensate for misalignment between the driveshaft means and said driven shaft;

whereby parallel and angular misalignment are compensated for.

9. A drive assembly as in claim 8 wherein said coefficient of frictionmaintaining means comprises means for lubricating the splines on saidtubular element whereby said tubular element rocks preferentiallyrelative to said adapter element and said outer drive shaft.

10. A drive assembly as in claim 9 further comprising means forscavenging oil from the splines on said outer drive shaft therebymaintaining a flow of lubricating fluid through said splines.

11. A drive assembly as in claim 10 wherein said scavenging meanscomprises a plurality of radially directed passageways extending fromthe minor diameter of the internal splines on said outer drive shaft tothe outer periphery thereof.

12. A drive assembly as in claim 11 further comprising: a

a housing surrounding said drive shaft and having an opening inalignment with said first end of said outer drive shaft;

means for sealing the periphery of the first end of said outer driveshaft relative to said housing;

means for sealing the tubular element relative to the outer drive shaftat a point between the internal splines of said outer drive shaft andthe first end v thereof; t 7

means for sealing saidannular adapter element relative to said tubularelement at a point between the internal splines of said tubular elementand the end of said tubular element adjacent the first end of said outerdrive shaft.

13. A drive assembly as in claim 12 further comprising means on bothends of said outer drive shaft assem- 45 bly for restraining axialmovement of said tubular element and said adapter element.

1. A drive assembly comprising: a drive shaft having a bore at an outerfacing end thereof and internal splines formed in said bore; an annularadapter element received in said drive shaft bore and having externalsplines interfitting with the internal splines formed in said driveshaft bore; said adapter element also having a bore with internalsplines formed therein to interfit with external splines of a drivenshaft receivable in said adapter bore; means for maintaining thecoefficient of friction between the drive shaft splines and the adapterelement external splines substantially lower than the coefficient offriction between the adapter element internal splines and the splines ofsaid driven shaft, said means comprising means for supplying lubricantto the interfitting internal splines of said drive shaft and theexternal splines of said adapter element whereby the adapter elementrocks preferentially relative to the drive shaft to compensate formisalignment between the drive shaft means and said driven shaft.
 2. Adrive assembly as in claim 1 further comprising means for scavenging oilfrom said internal splines of said drive shaft whereby a flow oflubricating fluid passes through the splines of said drive shaft.
 3. Adrive assembly as in claim 2 wherein said scavenging means comprises aseries of passageways extending generally radially outward from theminor diameter of the internal splines to the exterior periphery of saiddrive shaft whereby the splines of said drive shaft and the outersplines of said adapter element are substantially immersed inlubricating fluid.
 4. A drive assembly as in claim 1 further comprising:a housing surrounding said drive shaft means and having an annularopening substantially in line with the outer facing end of said driveshaft; means for sealing the outer periphery of said drive shaftrelative to the opening in said housing thereby preventing leakage oflubricating fluid past the outer periphery of said drive shaft; andmeans for sealing the outer periphery of said adapter element relativeto the bore of said drive shaft whereby the external splines on saidadapter element and the internal splines on said drive shaft areimmersed in lubricating fluid.
 5. A drive assembly as in claim 4 furthercomprising: a flange formed at the outer end of said adapter element forabutting the outer facing end of the said drive shaft; and a retainingflange releasably secured over the outer facing end of said drive shaftfor restraining movement of said adapter away from the outer facing endof said drive shaft.
 6. A drive assembly as in claim 5 wherein saidadapter element is formed from a sleevelike element having a circulardisk secured to the inner end of said element for preventing flow of oilto the internal splines of said adapter.
 7. A drive assembly as in claim6 wherein: said dRive shaft has a series of radially directed holesextending from the minor diameter of the internal splines of said driveshaft to the exterior periphery thereof; said lubricating meanscomprises a jet adapted to discharge a supply of lubricating fluidagainst the exterior of said drive shaft at a position spaced from saidsplines, said drive shaft having a generally radial opening in line withsaid jet thereby permitting flow of lubricating fluid to the interiorbore of said drive shaft.
 8. A drive assembly comprising: an outerelongated annular drive shaft having a first end adjacent said adapterelement and having a plurality of internal splines formed at a secondend axially spaced from said first end; an elongated tubular elementreceived in the interior of said outer drive shaft and having exteriorsplines at one end interfitting with the interior splines on said outershaft and inwardly directed splines at the opposite end thereof; anannular adapter element received in said tubular element at the oppositeend thereof and having external splines interfitting with the internalsplines formed in said drive shaft bore; said adapter element alsohaving a bore with internal splines formed therein to interfit withexternal splines of a driven shaft receivable in said adapter bore; andmeans for maintaining the coefficient of friction between the driveshaft splines and the adapter element external splines substantiallylower than the coefficient of friction between the adapter elementinternal splines and the splines of said driven shaft whereby theadapter element rocks preferentially relative to the drive shaft tocompensate for misalignment between the drive shaft means and saiddriven shaft; whereby parallel and angular misalignment are compensatedfor.
 9. A drive assembly as in claim 8 wherein said coefficient offriction maintaining means comprises means for lubricating the splineson said tubular element whereby said tubular element rockspreferentially relative to said adapter element and said outer driveshaft.
 10. A drive assembly as in claim 9 further comprising means forscavenging oil from the splines on said outer drive shaft therebymaintaining a flow of lubricating fluid through said splines.
 11. Adrive assembly as in claim 10 wherein said scavenging means comprises aplurality of radially directed passageways extending from the minordiameter of the internal splines on said outer drive shaft to the outerperiphery thereof.
 12. A drive assembly as in claim 11 furthercomprising: a housing surrounding said drive shaft and having an openingin alignment with said first end of said outer drive shaft; means forsealing the periphery of the first end of said outer drive shaftrelative to said housing; means for sealing the tubular element relativeto the outer drive shaft at a point between the internal splines of saidouter drive shaft and the first end thereof; means for sealing saidannular adapter element relative to said tubular element at a pointbetween the internal splines of said tubular element and the end of saidtubular element adjacent the first end of said outer drive shaft.
 13. Adrive assembly as in claim 12 further comprising means on both ends ofsaid outer drive shaft assembly for restraining axial movement of saidtubular element and said adapter element.